Probing the Mechanism of Seeded Growth of Highly-textured ZnO Nanostructures on Specific Surface Structures by the Solution Process
Chia-Hao Yu1*, Kuan-Hung Chen1, Shao-Sian Li1, Yih-Ren Chang1, Chun-Wei Chen1,2, Cheng-Yen Wen1,2
1Materials Science and Engineering, National Taiwan University, Taipei, Taiwan
2Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei, Taiwan
* presenting author:Chia-Hao Yu,
Highly-textured ZnO nanostructures are widely used in green energy industry, such as flexible energy-harvesting devices and optoelectronic energy devices. In order to grow textured ZnO nanostructures on arbitrary application substrates, a pretreatment on the substrate surface to form a textured-ZnO seed layer is often used. The temperature in this pretreatment method is usually higher than 250℃, at which some of the soft substrates may be damaged. In this study, we attempt to use a simple seedless solution process to grow ZnO nanostructures directly on substrates at a lower process temperature. We find that highly-textured ZnO nanostructures can grow on substrates with specific surface conditions, such as the hydrophobic surface of polyester and silicone. Furthermore, highly-textured ZnO nanostructures can also be directly grown on the silicon substrate surface terminated by the methyl functional group, prepared by the self-assembly monolayer (SAM) technique. In the latter growth case, the methyl group-ended silicon substrates are soaked in the nutrient solution for ZnO growth. It is observed that 1.5-nanometer thick zinc compound layer in a size of a few hundred nanometers are nucleated in a shape of triangles, with the c-axis of ZnO normal to the growth surface. The formation of the nucleation layer is ascribed to an adequate surface energy or the van der Waals epitaxy growth. It is expected that, after finding out the critical surface conditions for forming the nucleation layer, highly-textured ZnO nanostructures could be grown directly on arbitrary substrates using the solution-based process with extremely minimized thermal and lattice mismatch during their growth.

Keywords: Zinc oxide, Surface modification, Nucleation, Texture, Solution process